Balloon catheters are widely used in the medical profession for various intraluminal procedures. One common procedure involving the use of a balloon catheter relates to angioplasty dilation of coronary or other arteries suffering from stenosis (that is, a narrowing of the arterial lumen that restricts blood flow).
Although balloon catheters are used in many other procedures as well, coronary angioplasty using a balloon catheter has become particularly attractive to the medical community because of the growing number of people suffering from heart problems associated with stenosis. This has led to an increased demand for medical procedures to treat such problems. The widespread frequency of heart problems may be due to a number of societal changes, including the tendency of people to exercise less while eating greater quantities of unhealthy foods, in conjunction with the fact that people generally now have longer life spans than previous generations. Angioplasty procedures have become a popular alternative for treating coronary stenosis because angioplasty procedures are considerably less invasive than other alternatives. For example, stenosis of the coronary arteries has traditionally been treated with bypass surgery. In general, bypass surgery involves splitting the chest bone to open the chest cavity and grafting a replacement vessel onto the heart to bypass the blocked, or stenosed, artery. However, coronary bypass surgery is a very invasive procedure that is risky and requires a long recovery time for the patient.
To address the increased need for coronary artery treatments, the medical community has turned to angioplasty procedures, in combination with stenting procedures, to avoid the problems associated with traditional bypass surgery. Typically, angioplasty procedures are performed using a balloon-tipped catheter that may or may not have a stent mounted on the balloon (also referred to as a stented catheter). The physician performs the angioplasty procedure by introducing the balloon catheter into a peripheral artery (commonly one of the leg arteries) and threading the catheter to the narrowed part of the coronary artery to be treated. During this stage, the balloon is uninflated and collapsed onto the shaft of the catheter in order to present a low profile which may be passed through the arterial lumens. Once the balloon is positioned at the narrowed part of the artery, the balloon is expanded by pumping a mixture of saline and contrast solution through the catheter to the balloon. As a result, the balloon presses against the inner wall of the artery to dilate it. If a stent is mounted on the balloon, the balloon inflation also serves to expand the stent and implant it within the artery. After the artery is dilated, the balloon is deflated so that it once again collapses onto the shaft of the catheter. The balloon-tipped catheter is then retracted from the body. If a stent is mounted on the balloon of the catheter, the stent is left permanently implanted in its expanded state at the desired location in the artery to provide a support structure that prevents the artery from collapsing back to its pre-dilated condition. On the other hand, if the balloon catheter is not adapted for delivery of a stent, either a balloon-expandable stent or a self-expandable stent may be implanted in the dilated region in a follow-up procedure. Although the treatment of stenosed coronary arteries is one common example where balloon catheters have been used, this is only one example of how balloon catheters may be used and many other uses are also possible.
One problem that may be encountered with conventional angioplasty techniques is the proper dilation of stenosed regions that are hardened and/or have become calcified. Stenosed regions may become hardened for a variety of reasons, such as the build-up of artherosclerotic plaque or other substances. Hardened regions of stenosis can be difficult to completely dilate using conventional balloons because hardened regions tend to resist the expansion pressures applied by conventional balloon catheters.
It is also known to use cutting or scoring balloons in order to cut away at plaque and other build-up on the interior walls of a lumen. Examples can be found in the applicant's own earlier U.S. Pat. No. 7,303,572, as well as in U.S. Pat. No. 5,620,418 and US-2005/0137615. Cutting balloons can be a very effective way to remove plaque and other build-up in a vessel via an endoluminal procedure, particularly in conjunction with a filter for trapping the removed material. They provide a rapid and effective medical procedure with few or none of the side effects of open surgery procedures of the type highlighted above.
There are problems, however, with such cutting balloons, particularly related to their manufacture. Some forms of cutting balloon provide for the fixing onto the surface of the balloon of cutting elements, such as blades. This is a laborious process which furthermore results in a cutting balloon with limited compressibility, making it unsuitable for some medical applications.
Other forms of cutting balloon mould cutting protrusions into the surface of the balloon. However, heretofore this has not been an entirely successful task for several reasons. First, balloon catheters are stretched by inflation during manufacture as well as during use, with the result that surface irregularities including protrusions in the material tend to stretch and thus flatten. Attempts to solve this problem by making the protrusions of thicker material do not resolve the problem entirely and also add bulk to the balloon catheter and thus hinder its compressibility.